Method of synchronization and stimulation by means of pulse pairs at implanted heart stimulators with constant rhythm and the circuit for implementation of this method

ABSTRACT

An external rhythm frequency generator is magnetically coupled to a constant rhythm frequency generator of an implanted heart stimulator through an induction coil to provide either externally synchronized pulse pair stimulation or acceleration of the stimulator dependent on the frequency of a signal from the external generator. A relay is provided to control the flow of energy through the coil. A capacitive charging network is provided which discharges through the coil to create an electromagnetic field when the relay is operated. The relay is operated by a triggering circuit, which, in turn, operates the relay in synchronization with the emission of the signal from the external generator.

United States Patent Bukowiecki et al.

[m 3,659,616 [4 1 May 2,1972

[54] METHOD OF SYNCHRONIZATION AND STIMULATION BY MEANS OF PULSE PAIRSAT IMPLANTED HEART STIMULATORS WITH CONSTANT RHYTHM AND THE CIRCUIT FORIMPLEMENTATION OF THIS METHOD [72] inventors: Bohden A. Bultmvleclti,ul. L. Stafia l2/l4 M 23; Marius: Stopezyit, ul. 1.

Dabrowskiegv 86 m 71, both of Warsaw, Poland [22] Filed: Aug. 28, 1969[2i] Appl.No.: 853,883

OTHER PUBLICATIONS Cobbold et al. Medical Electronics & BiologicalEngineering," Vol. 3, No. 3,.luly, 1969, pp. 273- 277 Kantrowltz et ul.,Surgery, Gynecology & Obstetrics," Oct. i962,pp. 4i5- 420 Glass et ul.,American Heart Journal," Vol. 67, No. 1, Jan. 1964, pp. 137- 139 PrimaryExaminer-William E. Kamm Attorney-Hubbell, Cohen 8; Stiefel [57]ABSTRACT An external rhythm frequency generator is magnetically coupledto a constant rhythm frequency generator of an implanted heartstimulator through an induction coil to provide either externallysynchronized pulse pair stimulation or acceleration of the stimulatordependent on the frequency of a signal from the external generator. Arelay is provided to control the flow of energy through the coil. Acapacitive charging network is provided which discharges through thecoil to create an electromagnetic field when the relay is operated Therelay is operated by a triggering circuit, which, in turn, operates therelay in synchronization with the emission of the signal from theexternal generator.

8 Claims, 2 Drawing Figures Patentad May 2, 1972 2 Sham-Sheet 1.

Fig.4

METHOD OF SYNCI'IRONIZATION AND STIMULATION BY MEANS OF PULSE PAIRS ATIMPLANTIJ) HEART ST'IMULATORS WITH CONSTANT RHYTHM AND THE CIRCUIT FORIMPLEMENTATION OF THIS METHOD BACKGROUND OF THE INVENTION 1 Field of theInvention The present invention relates to a method and apparatus forproviding stimulation from an implanted heart stimulator having constantrhythm in synchronization with the emissions of a rhythm frequencygenerator located outside of a patients body.

2. Description of the Prior Art Up to now a frequency change oftriggering pulses from an implanted stimulator, or cardiac Pacemaker,having constant rhythm is accomplished by providing the stimulator witha two position relay built in the circuit of the rhythm frequencygenerator of the stimulator. The relay is controlled from outside of thebody of the patient by applying a magnet above the place of implantationof the stimulator.

This method enables a choice of only one of two triggering frequenciesestablished in advance for the given stimulator type. A steplessfrequency change of triggering pulses is obtained up to now only in animplanted stimulator provided with a control element led outside itshousing. This element is controlled by an instrument being introducedunder x-ray control into the stimulator after the puncture of the skinafter anaesthesia and disinfection.

In a stimulator having a constant rhythm which has no additional controlelements, a stepless frequency change of pulse triggering cannot beobtained.

In stimulators having a constant rhythm, clinical complications, such asan interference of stimulator pulses with a rudimentary or naturalrhythm of the heart of a patient, occur. In such cases the constancy ofstimulation frequency and impossibility of its changing to adapt it tothe actual electric activity of the heart is a defect which is dangerousto the life of the patient.

The method of heart stimulation with pulse pairs is the only method ofelectrocardiotherapy which influences not only the heart rhythm but alsoits mechanics of heart systole. Due to the influence upon mechanicalcoupling, pulse pair stimulation makes it possible to increase the forceof the heart systole and at the same time the slowing of its rhythm.

Pulse pair stimulation is normally utilized after reanirnation, forcirculatory inefficiency, cardiogenic shocks and after cardio-surgicaloperations. Up to now the heart stimulation is induced by means of pulsepairs with appliances located outside the patient. The implanted heartstimulators known up to now are not capable of inducing stimulation bymeans of pulse pairs.

The present invention overcomes these disadvantages of the prior art.

SUMMARY OF THE INVENTION A circuit is provided which enables externalsynchronization of the triggering of stimulating pulses and astimulation by pulse pairs from an implanted heart stimulator having aconstant rhythm frequency generator. An induction coil is magneticallycoupled to the stimulator generator. The coil is connected in thecircuit which includes a capacitive charging network. The circuit isonly completed when a relay is operated. An external rhythm frequencygenerator is connected to a Schmitt trigger which in turn operates therelay when a signal is emitted by the external generator. When thecircuit is completed, the charging network discharges through the coilwhich thereby generates an electromagnetic field. This field BRIEFDESCRIPTION OF THE DRAWING FIG. I is a schematic diagram of thepreferred embodiment of the present invention; and

FIG. 2 is a graphical illustration exemplary of the operation oftheembodiment shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to thedrawings in detail, and especially to FIG. I thereof. As shown andpreferred, the circuit of the present invention. generally referred toby the reference numeral 100, includes a supply circuit 1. The supplycircuit 1, preferably includes a power transformer 13 having a primaryl4, and a pair of secondary windings 16 and 18. Secondary winding 18 ispreferably connected at one end thereof to a diode 20 whose output isconnected to an electrolytic capacitor 22 to provide a conventionallow-voltage power supply. Similarly, secondary winding 16 is preferablyconnected at one end thereof to a diode 24 whose output is connected toan electrolytic capacitor 26 to provide another conventional powersupply. The supply apparatus 1 power supply 16-24-26 is preferablyconnected to a capacitive charging network 2 to supply power thereto.The capacitive charging network 2, preferably includes aresistor-capacitor combination of a resistor l2 and a capacitor 10. Thecharging network 2 is in turn connected to an electromagnetic fieldpower generator 3. The electromagnetic field power generator 3preferably includes a resistor ll, an induction coil 4 and an armatureportion 9 of a relay 8. The relay 8 also includes a solenoid 28connected in another portion of the circuit 100 as described in greaterdetail hereinafter. Preferably, the relay 8 acts as a switch to open andclose the circuit to the coil 4 and discharge capacitor 10 therethroufliin a manner to be described in greater detail hereinafter. The inductioncoil 4, is preferably located outside the patient's body above the placewhere the heart stimulator 31 is implanted, so as to be magneticallycoupled to the constant rhythm frequency generator of the stimulator 31to enforce the-generation of pulses therefrom.

The supply apparatus 1 low-voltage power supply 18-20-22 is connected toa rhythm frequency generator circuit 5. As shown and preferred, therhythm frequency generator 5 is a conventional blocking oscillatorconfiguration 5, and will not be explained in greater detailhereinafter. Suffice it to say, the operating frequency of theoscillator, or rhythm frequency generator 5 is controlled by means ofpotentiometer 7. The output of the rhythm frequency generator 5 ispreferably connected to a triggering network 6. The triggering network 6preferably includes a conventional Schmitt trigger configuration 30connected to the generator 5 output and an output stage 32 connected tothe output to the Schmitt trigger configuration 30. As shown andpreferred, the output stage 32 includes a transistor 34 having anemitter 36, a base 38 and a collector 40. The solenoid portion 28 of therelay 8, whose armature portion 9 forms parts of the electromagneticfield power generator 3 as was previously mentioned, is connected to thecollector 40 of the transistor 34 to receive a signal therefrom andactuate the relay 8.

OPERATION Now the operation of the circuit 100 will be described. Whenthe rhythm frequency generator 5 emits a signal, this signal controlsthe triggering unit 6 and causes the output transistor 34 to conduct,thereby providing a signal to the solenoid 28 of relay 8. This causesthe operation of the relay 8. The operation of the relay 8 causes theclosing of contacts 9 which completes the circuit to the electromagneticfield enforces the generation of a signal from the stimulator. Thispower generator 3. Thiscauses the capacitor 10 of the capacisignal is insynchronization with the emitted external signal and provides eitherpulse pair stimulation if the frequency of the external signal is lowerthan that of the stimulator, or acceleration of the stimulator if theexternal signal frequency is higher.

cally coupled rhythm frequency generator of the implanted stimulator andthus enforces the generation by the stimulator of a stimulating pulse,in synchronization with the emission of the signal from the rhythmfrequency generator 5.

At an operating frequency of the rhythm frequency generator 5 higherthan the set frequency of the implanted stimulator a synchronicacceleration of the operation of the stimulator 31 is provided.

On the other hand, at an operating frequency of the rhythm frequencygenerator 5 lower than the set pulse frequency of the implantedstimulator a stimulation by pulse pairs is provided.

Referring now to FIG. 2, we shall describe an illustrative example ofthe operation of the circuit 100 of the present invention. Assuming thefixed rhythm frequency of the stimulator to be represented by a timeinterval between pulses of T1 as shown in FIG. 2, a pulse 43 is enforcedby the circuit in accordance with the present invention. After the timeT1 the implanted stimulator generates its own pulse 44. Afier the timeT2, which represents the period of the rhythm frequency generator 5 ascounted similarly as the time T1 from the beginning of the pulse 43, apulse 45 is again enforced. Then the stimulator generates its own pulse46 and the circuit, in accordance with the present invention, enforces apulse 47.

As a result, we obtain pairs of stimulating pulses with a repeatingfrequency equalling the established frequency of the operation of theimplanted stimulator and the time interval between the pulses of thepair equalling the difference of times TI and T2. Time T2 changes withthe change of the period of the rhythm frequency generator 5. Throughthe controlled change of time T2 the interval between the pulses of thepair is controlled.

It is evident that the invention is not limited only to the embodimentdescribed in detail and represented in the drawing, but it comprisesalso the synchronizing of the operation of the implanted stimulators,whose rhythm frequency is controlled by the electric action of thechambers or vestibules of the heart.

What is claimed is:

l. A method for providing external synchronization of an additionalheart stimulation from an implanted heart stimulator having a constantrhythm frequency generator which normally provides heart stimulations ata predetermined constant rhythm frequency, said stimulator generatorhaving a predetermined period between said normally providedstimulations, said method comprising the steps of:

generating an independent external signal at a desired rhythm controlfrequency which is less than the constant rhythm frequency of thestimulator generator, the period of said external signal being greaterthan the period of said stimulator generator;

providing an electromagnetic field from said external signal insynchronization with said signal; and

enforcing a generation of said additional stimulation from saidgenerator in accordance with the provision of said electromagnetic fieldwhereby pulse pair stimulation is provided.

2. A method in accordance with claim I, wherein said enforcing stepincludes the step of magnetically coupling said stimulator generatorwithin said elecu'omagnetic field.

3. An apparatus for providing external synchronization of an additionalheart stimulation from an implanted heart stimulator having a constantrhythm frequency generator which normally provides heart stimulations ata predetermined constant rhythm frequency, the period between saidnormally provided stimulations being constant, said apparatus comprismg:

means for generating an independent external signal at a desired rhythmcontrol frequency which is less than the predetermined constant rhythmfrequency, the period of said external signal being greater than theperiod of said stimulator generator, and means for providing anelectromagnetic field from said external signal in synchronization withsaid signal, said providing means being magnetically coupled to saidstimulator generator, said stimulation being enforced from saidstimulator generator in accordance with said provided field wherebypulse pair stimulation is provided.

4. An apparatus in accordance with claim 3, wherein said providing meansincludes means for storing a signal charge, means for discharging saidstorage means operatively connected to said storage means,electromagnetic means operatively connected to said discharge means andmagnetically coupled to said stimulator generator, said discharge meansdischarging said storage means through said electromagnetic means insynchronization with the generation of said external signal, wherebysaid field is provided.

5. An apparatus in accordance with claim 4 wherein said providing meansfurther includes means for triggering the discharge of said storagemeans by said discharge means in synchronization with the generation ofsaid external signal, said triggering means being operatively connectedbetween said discharge means and said generation means.

6. An apparatus in accordance with claim 4, wherein said electromagneticmeans includes an inductive impedance and a resistive impedance.

7. An apparatus in accordance with claim 3, wherein said generationmeans is a blocking oscillator.

8. An apparatus in accordance with claim 3, wherein said storage meansis a capacitive charging network including a capacitive impedance and aresistive impedance.

1. A method for providing external synchronization of an additionalheart stimulation from an implanted heart stimulator having a constantrhythm frequency generator which normally provides heart stimulations ata predetermined constant rhythm frequency, said stimulator generatorhaving a predetermined period between said normally providedstimulations, said method comprising the steps of: generating anindependent external signal at a desired rhythm control frequency whichis less thaN the constant rhythm frequency of the stimulator generator,the period of said external signal being greater than the period of saidstimulator generator; providing an electromagnetic field from saidexternal signal in synchronization with said signal; and enforcing ageneration of said additional stimulation from said generator inaccordance with the provision of said electromagnetic field wherebypulse pair stimulation is provided.
 2. A method in accordance with claim1, wherein said enforcing step includes the step of magneticallycoupling said stimulator generator within said electromagnetic field. 3.An apparatus for providing external synchronization of an additionalheart stimulation from an implanted heart stimulator having a constantrhythm frequency generator which normally provides heart stimulations ata predetermined constant rhythm frequency, the period between saidnormally provided stimulations being constant, said apparatuscomprising: means for generating an independent external signal at adesired rhythm control frequency which is less than the predeterminedconstant rhythm frequency, the period of said external signal beinggreater than the period of said stimulator generator, and means forproviding an electromagnetic field from said external signal insynchronization with said signal, said providing means beingmagnetically coupled to said stimulator generator, said stimulationbeing enforced from said stimulator generator in accordance with saidprovided field whereby pulse pair stimulation is provided.
 4. Anapparatus in accordance with claim 3, wherein said providing meansincludes means for storing a signal charge, means for discharging saidstorage means operatively connected to said storage means,electromagnetic means operatively connected to said discharge means andmagnetically coupled to said stimulator generator, said discharge meansdischarging said storage means through said electromagnetic means insynchronization with the generation of said external signal, wherebysaid field is provided.
 5. An apparatus in accordance with claim 4wherein said providing means further includes means for triggering thedischarge of said storage means by said discharge means insynchronization with the generation of said external signal, saidtriggering means being operatively connected between said dischargemeans and said generation means.
 6. An apparatus in accordance withclaim 4, wherein said electromagnetic means includes an inductiveimpedance and a resistive impedance.
 7. An apparatus in accordance withclaim 3, wherein said generation means is a blocking oscillator.
 8. Anapparatus in accordance with claim 3, wherein said storage means is acapacitive charging network including a capacitive impedance and aresistive impedance.